If you've ever thought of bringing a second cat home as a companion for your first kitty, you may have been frightened off by friends' graphic tales of fighting and fur-flying.
Don't be discouraged just because the initial introduction may not be easy. Cats are territorial, and you have to respect that and do the introduction in a way that allows both the resident cat and the newcomer to feel secure.
1) Prepare a sanctuary room. The newcomer will initially need a room of his own. This is an important step to help him get his bearings and create a feeling of security when he first enters this unfamiliar environment. It also helps reduce your resident cat's feelings of being threatened, because the newcomer's presence will be limited to one specific area. Place a Feliway Comfort Zone diffuser in the newcomer's room, and one in your resident cat's main area.
2) Don't rush things. Before you attempt an actual introduction, let the newcomer get to know his sanctuary room, because this environment is totally unfamiliar to him. Let your resident cat get used to the idea that someone is in her house, but is not an immediate threat. During the actual introduction, continue to take things slowly.
3) Create positive associations. Here's the secret to doing a successful introduction: give the cats a reason to like each other! Let them see each other for very brief periods while being offered something irresistible, such as a treat or a meal. Keep them far enough apart so each kitty feels comfortable. As soon as they've eaten, separate them again and do another session later.
4) Never leave cats to "fight it out." You may have heard this advice from friends. But it's counter-productive and dangerous! There's no reason why either kitty should feel so threatened that they resort to battle. Do brief introduction sessions using positive associations to build in them a tolerance for each other, with minimal stress. Keep an interactive toy handy to use for distraction if things get tense. Da Bird is a great toy for that.
5) Create an environment for two. It's stressful when there isn't enough room for both cats. Even a small apartment can be large enough, if you allow for each cat's preferences. Don't ask them to share one litter box or eat out of one food bowl. Set up two litter boxes, scratching posts such as the Smart Cat post, and two feeding stations, as well as a few cozy napping areas or window perches.
Every introduction is unique, so don't be discouraged if your cats take a while to become friends. The biggest mistake I see is rushing the introduction. Invest the time now, so your cats can enjoy a lifetime of companionship. For more specific help on introductions, see the book Cat vs. Cat.